Fajan's Rule
Hello everyone , today I am going to write about Fajan's Rule
Fajans’ rules was formulated by American chemist of Polish origin Kazimierz Fajans (1887-1975), indicating the extent to which an ionic bond has covalent character caused by polarisation of the ions.
Covalent character is more likely if:
1. the charge of the ions is high;
2. the positive ion is small or the negative ion is large;
3. the positive ion has an outer electron configuration that is not a noble- gas configuration.
In an ionic solids there are cations and anions which are closely packed in a crystal in such a way that forces of attraction in oppositely charged ions overcome the force of repulsion in like ions. Let us consider 2 oppositely charged ions X + and Y - . Here charge density is higher on cation ( small size) than anion , therefore electron cloud of anion is electrostatically attracted by cation. As a result the anion Y - is polarized or deformed or distorted . The outer electron of anion Y - are attracted in middle of X + and Y - . It seems that electron is shared between 2 atoms , and hence imparts a slight covalent character to ionic bond . hence greater the polarization of anion , higher will be covalent character in ionic bond.
What is Fajan Rule of Polarisation?
To read more http://microamaze.blogspot.in/2015/12/fajans-rule.html
With love Dixy